android.support.v4.content.CursorLoader Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of support-v4 Show documentation
Show all versions of support-v4 Show documentation
The Support Package includes static "support libraries" that you can add to your Android application in order to use APIs that are either not available for older platform versions or that offer "utility" APIs that aren't a part of the framework APIs.
/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.support.v4.content;
import android.content.Context;
import android.database.ContentObserver;
import android.database.Cursor;
import android.net.Uri;
import java.io.FileDescriptor;
import java.io.PrintWriter;
import java.util.Arrays;
/**
* Static library support version of the framework's {@link android.content.CursorLoader}.
* Used to write apps that run on platforms prior to Android 3.0. When running
* on Android 3.0 or above, this implementation is still used; it does not try
* to switch to the framework's implementation. See the framework SDK
* documentation for a class overview.
*/
public class CursorLoader extends AsyncTaskLoader {
final ForceLoadContentObserver mObserver;
Uri mUri;
String[] mProjection;
String mSelection;
String[] mSelectionArgs;
String mSortOrder;
Cursor mCursor;
/* Runs on a worker thread */
@Override
public Cursor loadInBackground() {
Cursor cursor = getContext().getContentResolver().query(mUri, mProjection, mSelection,
mSelectionArgs, mSortOrder);
if (cursor != null) {
// Ensure the cursor window is filled
cursor.getCount();
registerContentObserver(cursor, mObserver);
}
return cursor;
}
/**
* Registers an observer to get notifications from the content provider
* when the cursor needs to be refreshed.
*/
void registerContentObserver(Cursor cursor, ContentObserver observer) {
cursor.registerContentObserver(mObserver);
}
/* Runs on the UI thread */
@Override
public void deliverResult(Cursor cursor) {
if (isReset()) {
// An async query came in while the loader is stopped
if (cursor != null) {
cursor.close();
}
return;
}
Cursor oldCursor = mCursor;
mCursor = cursor;
if (isStarted()) {
super.deliverResult(cursor);
}
if (oldCursor != null && oldCursor != cursor && !oldCursor.isClosed()) {
oldCursor.close();
}
}
/**
* Creates an empty unspecified CursorLoader. You must follow this with
* calls to {@link #setUri(Uri)}, {@link #setSelection(String)}, etc
* to specify the query to perform.
*/
public CursorLoader(Context context) {
super(context);
mObserver = new ForceLoadContentObserver();
}
/**
* Creates a fully-specified CursorLoader. See
* {@link android.content.ContentResolver#query(Uri, String[], String, String[], String)
* ContentResolver.query()} for documentation on the meaning of the
* parameters. These will be passed as-is to that call.
*/
public CursorLoader(Context context, Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
super(context);
mObserver = new ForceLoadContentObserver();
mUri = uri;
mProjection = projection;
mSelection = selection;
mSelectionArgs = selectionArgs;
mSortOrder = sortOrder;
}
/**
* Starts an asynchronous load of the contacts list data. When the result is ready the callbacks
* will be called on the UI thread. If a previous load has been completed and is still valid
* the result may be passed to the callbacks immediately.
*
* Must be called from the UI thread
*/
@Override
protected void onStartLoading() {
if (mCursor != null) {
deliverResult(mCursor);
}
if (takeContentChanged() || mCursor == null) {
forceLoad();
}
}
/**
* Must be called from the UI thread
*/
@Override
protected void onStopLoading() {
// Attempt to cancel the current load task if possible.
cancelLoad();
}
@Override
public void onCanceled(Cursor cursor) {
if (cursor != null && !cursor.isClosed()) {
cursor.close();
}
}
@Override
protected void onReset() {
super.onReset();
// Ensure the loader is stopped
onStopLoading();
if (mCursor != null && !mCursor.isClosed()) {
mCursor.close();
}
mCursor = null;
}
public Uri getUri() {
return mUri;
}
public void setUri(Uri uri) {
mUri = uri;
}
public String[] getProjection() {
return mProjection;
}
public void setProjection(String[] projection) {
mProjection = projection;
}
public String getSelection() {
return mSelection;
}
public void setSelection(String selection) {
mSelection = selection;
}
public String[] getSelectionArgs() {
return mSelectionArgs;
}
public void setSelectionArgs(String[] selectionArgs) {
mSelectionArgs = selectionArgs;
}
public String getSortOrder() {
return mSortOrder;
}
public void setSortOrder(String sortOrder) {
mSortOrder = sortOrder;
}
@Override
public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) {
super.dump(prefix, fd, writer, args);
writer.print(prefix); writer.print("mUri="); writer.println(mUri);
writer.print(prefix); writer.print("mProjection=");
writer.println(Arrays.toString(mProjection));
writer.print(prefix); writer.print("mSelection="); writer.println(mSelection);
writer.print(prefix); writer.print("mSelectionArgs=");
writer.println(Arrays.toString(mSelectionArgs));
writer.print(prefix); writer.print("mSortOrder="); writer.println(mSortOrder);
writer.print(prefix); writer.print("mCursor="); writer.println(mCursor);
writer.print(prefix); writer.print("mContentChanged="); writer.println(mContentChanged);
}
}